diff --git a/lib/node/valueExpression.js b/lib/node/valueExpression.js
index faad8033..2fa741a9 100644
--- a/lib/node/valueExpression.js
+++ b/lib/node/valueExpression.js
@@ -148,6 +148,7 @@ var ValueExpressionMixin = function() {
     at         : atMethod,
     contains   : binaryMethod('@>'),
     containedBy : binaryMethod('<@'),
+    containsKey : binaryMethod('?'),
     overlap    : binaryMethod('&&'),
     slice      : sliceMethod,
     cast       : castMethod,